JP2021503254A - Systems and methods for demodulating wavelength division multiplexing optical signals - Google Patents

Abstract

An optical signal receiver and a method for inputting and accumulating optical signal energies of a plurality of wavelengths in an optical resonator are provided. A portion of the optical signal energy of each wavelength is emitted from the optical resonator at the output, and the individual wavelengths may be separated. A detector aligned with the output detects the emitted optical signal energy of at least one of the wavelengths. The detector is configured to detect disturbances to the emitted optical signal energy and determine the modulation characteristics of the received optical signal energy of the wavelength.

Description

[Related application]
This application is incorporated herein by reference in its entirety for all purposes, both pending US Provisional Patent Application Nos. 62 / 587,696, named "SYSTEMS AND METHOD FOR DEMODULATION OF WAVE DIVISION MULTIPLEXED OPTICAL SIGNALS", 2017. Filed on November 17, 2014, 35 U.S.A. S. C. Claim the benefits of §119 (e) and Article 8 of the PCT.

Many optical signals include phase modulation formats, as well as amplitude and other modulation formats, which have certain advantages. The information encoded by phase modulation may include communication data to be transmitted, or information about the source of the optical signal, the interaction of the optical signal with obstacles, the optical channel through which the optical signal propagated, and / or each other. It may contain other information such as acting obstructions. Compared to standard amplitude modulated receivers, phase modulated receivers are much more complex, with precision optics, local oscillators, grids (eg Fiber Bragg Gratings), and / or delay line interferometers (delay). Line interferometers: DLI) etc. are required. Typically, a phase modulation receiver collects a phase coded optical signal and performs one or more demodulation processes to convert the phase modulation into a useful routine. In systems that utilize wavelength division multiplexing (WDM), including dense wavelength division multiplexing (DWDM), multiple optical signals are carried simultaneously at different wavelengths. WDM receiver systems for phase-modulated optical signals can therefore be significantly more complex and require multiple complex phase receivers to receive multiple wavelengths.

The embodiments and examples described herein provide systems and methods for simultaneous detection and demodulation of multiple, eg, different wavelength, optical signals that do not require a local coherent clock source. In particular, a particular example of a system is a receiver with an optical resonator, such as a Fabry-Perot filter / resonator, that converts multiple received optical wavelengths that may contain phase-encoded information into intensity-encoded optical wavelengths. Including. The individual wavelengths may be separated and the individual intensity coded optical signals may be fed to the receiver. The optical resonator may be tuned to match (a set of) wavelength sets of WDM optical signals and to function over a wide range over various wavelengths without the need to change the characteristics of the receiver. In addition, one or more optical cavities may be utilized to pass amplitudes and other changes from the received signal, converting them into intensity coded output signals, thereby higher order phase modulation schemes. , Amplitude modulation, and / or enable detection and reception of frequency modulation. Therefore, the systems and methods disclosed herein may provide flexibility to accommodate different coding techniques and different modulation rates (eg, baud rates) at each of the multiple wavelengths.

According to one embodiment, the optical signal receiver
An optical resonator having a hole for incident optical signal energy and an output for radiating a part of the optical signal energy.
The optical resonator receives optical signal energies of a plurality of wavelengths through the hole, stores the resonant optical signal energy inside the optical resonator, and stabilizes the optical signal energy radiated at each of the plurality of wavelengths. The optical resonator is configured to approach the state output intensity and disturb the radiated optical signal energy of each wavelength by a transition in the received optical signal energy of each wavelength, and the optical cavity has at least one dimension. Includes an optical resonator, which produces phase matching of the stored optical signal energy at each of the plurality of wavelengths. The optical signal receiver is an optical splitter that is configured to receive the radiated optical signal energy and separate the radiated optical signal energy into each of the plurality of wavelengths. ,
A detector that receives at least one of the plurality of wavelengths, detects the turbulence with respect to the radiated optical signal energy, and determines the transition characteristics of the received optical signal energy based on the turbulence. It further includes a detector that is configured.

In one example, the optical resonator is further configured to disturb the emitted optical signal energy based on a phase change in the received optical signal energy. In another example, the turbulence is a change in the intensity of the emitted optical signal energy, the detector detecting the change and determining a phase transition in the received optical signal energy based on the change. Is configured. In one example, the optical resonator has two semi-reflecting surfaces configured to trap at least part of the optical signal energy by reflecting a portion of the optical signal energy that collides with each of the semi-reflecting surfaces. Etalon. The optical resonator includes first and second reflecting surfaces, the first and second reflecting surfaces being substantially parallel to each other and having reflective sides facing each other, the first reflecting surface being the hole. At least a part of the above is formed, the optical signal energy arriving from the outside of the optical resonator is partially transmitted, the optical signal energy is input to the optical resonator, and the second reflecting surface is at least the output. A part of the optical signal energy is substantially reflected, but the part of the optical signal energy is partially transmitted to the inside of the optical cavity and radiated to the outside of the optical cavity. The optical resonator is input. The detector further comprises an opto-electrical converter configured to convert the radiated optical signal energy into an electrical signal, the optical signal having an amplitude indicating the intensity of the radiated optical signal energy. By processing the electrical signal, it is configured to detect interference with the radiated optical signal energy.

According to another embodiment, the method of detecting the information encoded in the optical signal is described in a step of receiving optical signal energy of a plurality of wavelengths and an optical resonator that brings the stored optical signal energy closer to a steady state. The step of accumulating the optical signal energy and the step of outputting the optical signal energy from the accumulated optical signal energy, the intensity of the output optical signal energy at each of the plurality of wavelengths is the above. In the step proportional to the stored optical signal energy of each wavelength, the step of detecting the output optical signal energy of at least one of the plurality of wavelengths, and the detected output optical signal energy. Based on the above, the step of determining the modulation characteristic of the received optical signal energy is included.

In one example, the step of determining the modulation characteristic of the received optical signal energy based on the detected output optical signal energy determines the phase change of the received optical signal energy based on the intensity change of the output optical signal energy. Includes steps to do. The method accumulates in the optical cavity by one of the weakening or strengthening interferences in the optical cavity in response to the modulation characteristic of the received optical signal energy. It further includes a step of changing the optical signal energy. In one example, the modulation characteristic of the received optical signal energy is a phase transition associated with each of the wavelengths. In another example, the step of accumulating the optical signal energy in the optical resonator includes a step of partially reflecting the optical signal energy between the two semi-reflecting surfaces. The method is a step of converting the output light signal energy into an electrical signal, further comprising a step in which the amplitude of the electrical signal represents the intensity of the output light signal energy. In one example, the step of determining the modulation characteristic of the received optical signal energy based on the detected output optical signal energy includes the step of supplying the electric signal to the receiver.

According to another embodiment, the optical receiver is an etalon, configured to at least partially store optical signal energies of multiple wavelengths between two semi-reflecting surfaces to input said optical signal energies. It has a hole and an output that radiates a part of the stored optical signal energy, and the etalon determines the intensity of the output optical signal energy based on the phase transition of the input optical signal energy. An etalon and an opto-electrical converter that are configured to be temporarily altered to receive at least one wavelength of the output optical signal energy and convert the received optical signal energy into an electrical signal. Includes an opto-electric converter and a receiver that is configured to receive the electrical signal and determine encoded information based in part on the electrical signal. ..

In one example, the optical receiver further comprises a converter configured to convert the electrical signal from an analog format to a digital format, and the receiver is configured to receive the electrical signal in the digital format. .. Another example further includes an optical splitter configured to receive the output light signal energy and separate the output light signal energy into each of the plurality of wavelengths. In one example, the optical splitter is an arrayed waveguide grid. In another example, the etalon is configured to have a reference dimension selected to at least partially store the optical signal energies of the plurality of wavelengths in the etalon. In another example, the etalon is a reference dimension selected to cause the accumulation of optical signal energy so that it occurs at a particular rate to correspond to the expected data rate associated with the encoded information. Is configured to have. The optical receiver further includes an optical system configured to collect the optical signal energy and supply the optical signal energy to the etalon.

Yet other aspects, examples, and advantages are discussed in detail below. The embodiments disclosed herein may be combined with other embodiments in any way that conforms to at least one of the principles disclosed herein. References to "one embodiment", "embodiments", "some embodiments", "alternative embodiments", "various embodiments", "certain embodiments", etc. are not necessarily mutually exclusive. , It is intended to indicate that the particular features, structures, or properties described may be included in at least one embodiment. The appearance of such terms in the specification of the present application does not necessarily refer to the same embodiment. The various aspects and embodiments described herein may include means of performing any of the methods or functions described.

Various aspects of at least one embodiment are discussed below with reference to the accompanying drawings which are not intended to be drawn to scale. The drawings are included to provide explanations and further understanding of various aspects and embodiments, which are incorporated into and part of the specification of the present application, but are not intended to be a limitation of the present disclosure. In the figure, each identical or nearly identical component shown in the various figures is indicated by similar reference numerals. For clarity, not all components may not be labeled in all figures. The figure is as follows.
FIG. 6 is a block diagram of a conceptual optical transmitter used with the various examples described herein. It is a block diagram of the optical resonator according to various examples described in the present specification. It is the schematic of the example of the optical resonator including the graph of the received signal phase and the graph of the output intensity of the optical resonator. It is a graph of the optical input phase and the output intensity from an example of the optical resonator of FIG. It is a schematic diagram of an example of an optical resonator operating at a plurality of wavelengths in which each wavelength is separated from other wavelengths. FIG. 6 is a schematic representation of another example of an optical resonator operating at multiple wavelengths, each wavelength separated from another wavelength. It is a schematic diagram of an example of an optical resonator operating at a plurality of wavelengths in which each wavelength is separated from other wavelengths and has different polarities. It is a schematic diagram of an example of a multi-wavelength multi-polar communication system using an optical resonator as a receiver component. FIG. 5 is a functional block diagram of an example of a control unit configured to implement various examples of the processes described herein.

Various embodiments and embodiments are intended for improved systems and methods for demodulating phase-coded (ie, phase-modulated) optical signals. In a particular example, the system includes an optical resonator such as a Fabry-Perot filter / cavity or microring that simultaneously converts a multi-wavelength phase-coded optical signal into a directly detectable intensity modulated output signal.

Phase-coded optical signals can come from multiple sources and / or be generated by multiple processes. Detection of phase coding can therefore be useful for many purposes. A coherent optical signal, such as a laser beam, may be deliberately modulated by a data communication transmitter, for example, to encode the information being communicated onto the optical signal. Other information, such as timing and / or timestamp information, may be intentionally encoded as phase modulation. A number of processes may phase-modulate a coherent light source, from which information about the process may be restored by appropriate demodulation (eg, interpretation) of the phase-modulated optical signal. For example, various measurement systems may transmit optical signals and analyze reflected signals to determine dimensions, movements, defects, and the like. Examples of various systems in which demodulation of phase-modulated optical signals may be advantageous include target indicators, laser guidance systems, laser sites, laser scanners, 3D scanners, home beacons, and / or survey systems, and communication systems. In various of these examples, the optical signal may arrive via a free space signal path (eg, free space optical, FSO) or fiber or other waveguide system. The systems and methods for demodulating phase-modulated optical signals according to aspects and examples disclosed herein are advantageously applied to the exemplary optical systems described above, or any of the others. It may receive useful information from an optical signal having phase coding, detect it, restore it, and so on.

It should be understood that the methods and equipment embodiments described herein are not limited to the configuration details and component arrangements described in the following description or illustrated in the accompanying drawings in the application. The methods and equipment can be implemented or implemented in a variety of ways, implemented in other embodiments. Examples of specific implementations are provided here for illustration purposes only and are not intended to be limiting. Also, the terminology and terminology used herein is for explanatory purposes only and should not be considered as a limitation. The use of "includes", "includes", "has", "includes", "related", and variations thereof herein includes the items listed below and their equivalents, as well as additional items. means. References to "or" may be considered inclusive, and as a result, any item described using "or" may be single, more than one, or all of the items listed. May be shown. Any references to the front and back, left and right, top and bottom, top and bottom, and vertical and horizontal are for convenience of explanation and any one of the systems and methods of the invention or components thereof. Not limited to positional or spatial directions.

Many optical communication receivers (eg, coherent receivers) require a stable clock to accurately perform demodulation processing on the received signal, and in particular modulation of information on the polarization of the optical signal. When including coding, advanced optics such as 90 degree hybrids, phase shifters, etc. may be required. In contrast, the optical receivers of the embodiments and examples disclosed herein do not require a local coherent clock source or important optical components to achieve the same receiving capabilities as conventional optical receivers. Benefits are achieved, at least in part, by an optical front end that includes an optical resonator that does not have a coherent reference source and can detect modulation transitions such as phase variation in an optical signal. The optical front end further transforms the modulation, eg, phase modulation, into intensity modulation, which in some cases allows for simple processing in the electrical domain.

FIG. 1 shows a functional block diagram of an example of a transmitter (for example, an optical transmitter 100), and FIG. 2 shows a functional block diagram of an example of a receiver (for example, an optical receiver 200). As will be immediately apparent to those skilled in the art who have benefited from the present disclosure, the transmitter shown in FIG. 1 may be combined with the receiver shown in FIG. 2 to provide an example of a communication assembly.

The components of the exemplary optical transmitter shown in FIG. 1 and the optical receiver shown in FIG. 2 may be shown and described as separate elements in the block diagram, “module”, “circuit”, or “circuit”. Unless otherwise indicated, a component may be implemented as an analog circuit, a digital circuit, or one or more microprocessors executing software instructions (eg, predetermined routines). In particular, software instructions may include digital signal processing (DSP) instructions. Unless otherwise indicated, the signal transition between the components of the optical transmitter 100 and the components of the optical receiver 200 may be implemented as separate analog, digital, or optical signal lines. Some of the processing operations may be represented in terms of calculation or determination by the optical transmitter 100, optical receiver 200, control unit, or other component. Calculation and determination of values, or equivalents of other elements, can be performed by any suitable analog or digital signal processing technique and are included within the scope of this disclosure. Unless otherwise indicated, the control signal may be encoded in digital or analog form.

Referring to FIG. 1, an example of an optical transmitter 100 includes an input 102 that receives a data payload, a light source (eg, a laser) 104, a modulator 106, and an optical system 108, and an output 110 that provides an optical signal output. Good. The modulator 106 imposes a modulation scheme on the light source 104 that produces the modulated optical signal. In various examples, the modulator 106 may be an electrical-optical modulator and may include a light source 104 such as a laser. In particular, for each symbol of the data payload, the light source 104 may radiate a continuous carrier waveform that is modulated (in phase, amplitude, and / or frequency) in order to encode these symbols into carrier waveforms. The transmitter 100 may also include various optical systems 108 such as one or more mirrors or lenses that direct an optical signal to the output 110.

FIG. 2 shows an example of an optical receiver 200 according to various examples discussed herein. FIG. 2 will continue to be described with reference to the optical transmitter 100 of FIG. 1 which may communicate the data payload to the optical receiver 200. In addition, the receiver and transmitter may be paired together, for example to form a transceiver, and bidirectional data communication with another transmitter / receiver pair is possible.

The illustrated receiver 200 includes an optical resonator 230 and a digital processing subsystem 250 that receives the optical signal 210 and provides an output of 270. The optical resonator 230 may be coupled to the digital processing subsystem 250 by, for example, an optical-electric converter 242 and an analog-to-digital converter 244.

Examples of the optical resonator 230 may include Fabry-Perot etalons, microrings, or other types of resonators. The optical resonator 120 is a component capable of detecting a transition such as a phase variation representing the modulation performed in the transmitter and converting the transition into an intensity modulation of an output light signal, eg, an output light signal 232. is there. The optical resonator 230 partially converts the modulation of the incoming optical signal 210 by the interaction between the incoming optical signal 210 and the resonant optical energy configured in the optical resonator 230.

For example, etalon is a component with a pair of parallel semi-reflecting surfaces. Parallel semi-reflective surfaces may contain a transparent material in between, each with one or more characteristic resonant frequencies associated with a particular wavelength of light based on the spacing (ie, dimensional length) between the semi-reflective surfaces. Have. The surfaces are both semi-reflective and semi-transparent, and these surfaces allow some light to pass through, so that the incoming light signal 210 can enter the etalon and resonate within the etalon (ie, two semi-reflectors). (Between faces). In addition, some of the internally resonating light is emitted outside the etalon (through the transflective surface). The light emitted from the etalon is shown, for example, as the optical signal 232 in FIG.

The optical signal received by the optical resonator 230, in this example the etalon, may establish steady-state energy conservation conditions in which the optical signal energy arrives continuously at the etalon, and is stored or stored inside the etalon. It is added to the resonant energy and exits the etalon at a constant rate. Changes in the incoming phase, frequency, or amplitude of the optical signal may disrupt the resonance within the etalon until steady-state conditions are reestablished, and also the intensity of light radiated from the etalon. Therefore, a change in the phase, frequency, or amplitude of the incoming light signal 210 causes a change in the intensity of the synchrotron radiation signal 232. A large phase transition of the incoming light signal 210 causes, for example, a large (but temporary) intensity change of the synchrotron radiation signal 232. Similar operation occurs in the microring or other optical resonator, and therefore the optical resonator 230 functions as a demodulator or modulation transducer for the optical signal 210. The synchrotron radiation signal 232, therefore, in intensity-modulated form, can carry the same information content as the incoming light signal 210.

The radiant intensity modulated optical signal 232 may be converted into an electrical signal by a light-electric converter, such as CEC242, which may include a photodetector such as a photodiode. Therefore, the output of the OEC 242 may be an amplitude modulated signal representing an intensity modulated optical signal 232 and may be converted to digital form by an analog-to-digital converter, such as the ADC 244. The digital signal is provided to the digital processing subsystem 250 for digital processing. The digital processing subsystem 250 processes the digital signal and receives the information carried by the optical signal 210.

In various examples, the receiver according to the aspects and examples disclosed herein may include more or less optics than described above, with various components omitted or added to those described above. For example, a focusing optical system may be included to receive the optical signal 232 radiated from the optical resonator 230 and to focus the optical signal 232 on the OEC 242. A particular example may use an analog receiver circuit, and therefore one or more of the ADC 224s may be omitted. Various examples may include a channel estimator as part of the digital processing subsystem 250 to provide phase rotation or other signal tuning that may be conventionally known.

As mentioned above, suitable optical resonators may include etalons, microrings, or other structures. Some details of at least one example of etalon will be described later with reference to FIG. A microring is a resonator in the form of one or more waveguides, at least one of which is a closed loop. As a result, the optical signal energy propagating "around" the loop can be aligned in size and phase with the loop at one or more frequencies. Therefore, the optical signal energy propagating in the loop may interfere with itself at a specific frequency to strengthen each other, and maintain the optical signal energy in the loop. At other frequencies, the optical signal energy propagating in the loop interferes with and weakens itself, thereby disrupting or rejecting the accumulation of optical signal energy at that frequency. A closed loop is also coupled with some kind of input that causes light to enter the loop, such as an aperture and an output that causes light to exit the loop.

FIG. 3 shows an example of an etalon 300 that can be used in various examples of receivers according to aspects and embodiments described herein, such as the optical resonator 230 of FIG. In particular, the receiver may use the Etalon 300 to convert the phase modulation of the received optical communication signal 310 into the intensity or amplitude modulation of the output optical signal 320. The intensity or amplitude modulated output light signal 320 may then be converted into an electrical signal, the corresponding amplitude variation representing the mobile modulation of the received light signal 310. The etalon 300 causes the received optical signal 310 to have a resonance interaction with itself inside the etalon 300. As a result, the phase change of the received light signal 310 disrupts the resonance and causes an amplitude (or intensity) variation in the output light signal 320 that may be directly coupled to the detector.

In a particular example, the Etalon 300 is designed to have a resonant frequency aligned with the light source of the received optical communication signal 310, such as the transmitting laser. In various examples, the dimensional scale of the Etalon 300, eg, length 302, is selected such that the Etalon 300 exhibits optical resonance at the wavelength of the received optical communication signal 310. In a particular example, such a dimensional scale is much shorter than the length of the transmitted symbol and is the distance that the optical signal propagates during information-carrying transitions, such as during phase changes.

The Etalon 300 includes an interior 304 with semi-reflective surfaces 306, 308 that reflect light signal energy into the interior 304. The input side 312 causes an optical signal energy such as an optical communication signal 310 to enter the interior 304. The input side 312 thereby forms a hole. The incoming optical communication signal 310 is received through the hole. The output side 322 forms an optical output that radiates a part of the optical signal energy trapped from the interior 304 as an output optical signal by the operation of the semi-reflecting surface 306, at least partially. Therefore, the semi-reflecting surface 306 is also semi-transparent. As a result, the optical signal energy arriving at the transflective surface 306 (from the interior 304) is partially reflected back to the interior 304 and partially transmitted to the output side 322. The etalon 300 may have varying reflectance levels of the semi-reflective surfaces 306, 308. In certain examples, reflectance may be expressed as a function of the amplitude of the light reflected back to the interior 304, or as part of the intensity of the light reflected back into the interior 304. In a particular example, the amplitude reflectance of the first semi-reflective surface 308 may be r ₁ = 0.999 and the amplitude reflectance of the second semi-reflective surface 306 may be r ₂ = 0.985. .. In other examples, the reflectances of the first and second semi-reflecting surfaces may be different and may be any suitable value for a particular implementation. The Etalon 300 is an example of a suitable optical resonator according to the embodiments and embodiments described herein.

According to a particular example, an optical resonator such as the Etalon 300 coherently expands the output signal based on the input signal and maintains a given level of the output signal until phase modulation of the input signal occurs. When phase modulation occurs in the input signal, self-interference (strengthening or weakening) can cause a phase-dependent change in the amplitude of the output signal. This can be seen in the input phase plot 330 and the output power plot 340 shown in FIG. Therefore, the received phase-coded optical communication signal such as the received optical signal 310 is converted into a signal having a variable amplitude such as the output optical signal 320 by an optical resonator such as the Etalon 300. The output optical signal 320 is suitable for direct detection by a sensor such as the OEC 242 of FIG. In addition, the optical resonator functions over a wide range of data rates without the need to change the system's optical characteristics such as detector settings, path length adjustments, delay factors, and so on. For example, the ability of the Etalon 300 to convert an incoming phase modulated input optical signal 310 into an intensity modulated output optical signal 320 may be independent of the modulation rate at which the input phase changes in some examples.

The use of the term "etalon" throughout the present disclosure is not intended to be limited and, as used herein, includes a plate with a reflective surface and a parallel mirror with various materials in between. It may include any of a plurality of structures and may be referred to as a cavity, interferometer, etc. In addition, the etalon structure may be formed as a laminate, layer, film, coating, etc.

FIG. 3 shows the operation of the Etalon 300 with reference to the output power plot 340 of the optical signal intensity (as the output power) radiated from an optical resonator such as the Etalon 300 during the phase transition 332 of the received optical signal 310. Further shown. At point 342, the etalon 300 is in steady-state resonant conditions, and the steady-state intensity of light appears. At point 344, a phase transition 332 occurs at the incoming light signal 310, temporarily disrupting the steady state and causing a change in synchrotron radiation intensity. During the continuous reflections inside the etalon labeled point 346, the resonance was reestablished and when the etalon 300 returned to steady-state conditions, the synchrotron radiation intensity remained until the steady-state intensity of light appeared at point 348. Increase.

Therefore, fluctuations in the emission intensity from an optical resonator such as the Etalon 300 or Microring indicate that a transition such as a phase, frequency, or amplitude variation has occurred in the incoming light signal, and thus the emission intensity. It may be used with appropriate signal processing to determine useful information by analysis. In the example shown above and in FIG. 3, the incoming light signal 310 is presumed to be phase modulated, while other examples include frequency or amplitude modulation, or a combination thereof, similar in output intensity. It may cause variability or other detectable variability. In some examples, higher order or more complex modulations may be made by various optical resonator designs.

As a particular example, the etalon tuned to the incoming wavelength responds to the phase variation of the incoming optical signal described above and in FIG. When the incoming light signal is modulated by binary phase shift keying (BPSK), for example, the output shown in FIG. 3 shows each phase shift, and therefore the information carried by phase shift keying , It may be restored from the intensity fluctuation in the output optical signal 320. It should be understood by those skilled in the art who have the benefit of the present disclosure that such information restoration is achieved without the need for a local coherent clock source to demodulate the incoming optical signal.

FIG. 4 shows a plot 410 of the changing phase of the received phase-modulated optical signal and a plot 420 of the intensity resulting from the output optical signal from an optical resonator such as the Etalon 300. The result shown in FIG. 4 is that of an etalon having a length of 18 μm and having a reflectance of 0.999 on the semi-reflective surface 308 and 0.985 on the semi-reflective surface 306. The other continuous input phase (indicated by plot 410) changes at intervals according to the modulated information content, and plot 410 appears as a sequence of binary data such as high and low bits corresponding to 1 and 0, for example. Of the plurality of phase transitions shown in plot 410, the phase transition 412 is specifically associated with the change 422 in output intensity shown in plot 420. Each phase variation in the received optical signal causes a change in the output intensity. Therefore, the receiver can track changes in output intensity, thereby restoring the information content of the received phase-modulated optical signal.

Optical cavities such as etalons and microrings that demodulate optical signal modulation or convert it to intensity modulated output signals, as discussed herein, can act simultaneously on multiple wavelengths. The optical cavity therefore transforms the modulation of multiple wavelength signals within one cavity, for example for systems using wavelength division multiplexing (WDM), including coarse WDM and dense WDM. You can do it. For example, one or more optical resonators may act on the incoming WDM signal before the WDM signal is separated into their various wavelengths. "Phase or other variation at any number of incident wavelengths" can be detected simultaneously and converted into output intensity modulation for each wavelength.

FIG. 5A shows an example of a part 500a of the receiver system. Multiple wavelengths of light 502 enter etalon 504. The etalon 504 includes a resonant cavity that stores energy from each of the incident wavelengths 502. The etalon 504 is a linear device and therefore does not result in mixing or heterodining of individual wavelengths 502. The various wavelengths 502 of light interact individually with Etalon 504 as described above. As a result, each of the wavelengths 502 radiates from the etalon 504 as an intensity modulated light signal 506. The wavelength-based optical splitter 508 then separates the light into its own individual wavelengths to provide a separated intensity-modulated optical signal 510, each of which is its own wavelength. Each of the wavelengths of the separated intensity-modulated optical signal 510 may be received by a detector 512, such as an optical-electric converter that converts each wavelength into, for example, an electrical signal. In some examples, the detector 512 may be a detector array that may include a large number of photodetectors.

Each of the output electrical signals from the detector 512 contains an amplitude variation that indicates a modulation variation of one of the wavelengths of light, for example as described above with respect to FIG. For example, when in steady state, the light exiting Etalon 504 has a constant intensity at each wavelength. When phase variation occurs in light of a particular wavelength, the intensity of that wavelength exiting Etalon 504 is temporarily altered (eg, increased or decreased) by an amount related to the amount of phase variation. Each detector 512 that converts a particular wavelength produces an electrical signal whose amplitude is temporarily changed according to a temporary change in light intensity.

In some examples, different optical resonators may be used in place of the Etalon 504. For example, the microring may be used as an optical resonator, as described above, without departing from the exemplary portion 500a shown in FIG. 5A. Further, the photosplitter 508 that separates light by various wavelengths may be any of various light or photon devices such as a simple prism. In some examples, the splitter 508 may be an arrayed waveguide grating (AWG).

FIG. 5B shows another example of a portion 500b of a receiver system similar to the portion 500a of FIG. 5A. Part 500b includes an arrayed waveguide grid 508a that separates the light into its various wavelengths. In some examples, the arrayed waveguide grid 508a may have a fiber optic interface. In the example of FIG. 5B, the incoming light 502 may come from free space, and the intensity-modulated synchrotron radiation 506a from the Etalon 504 passes through a focusing element 514 such as a lens to direct the light 506b to the fiber optic interface. May be in focus. In another example, the incoming light 502 may arrive at the optical fiber and the etalon 504 may be in the line between the incoming optical fiber and the optical fiber interface. Therefore, the converted intensity-modulated light 506a enters the optical fiber interface directly. In some examples, the arrayed waveguide grid 508 may be a fiber coupled to various detectors 612.

As mentioned above, each of the multiple wavelengths of light can interact with an optical resonator such as an etalon or microring independently of the other wavelengths of light. For a particular wavelength of light, the maximum steady-state output occurs when the optical resonator is sized to resonate for a particular wavelength. Therefore, there may be optimal operating conditions for a particular wavelength of resonating light. Further, the optical resonator may generate or generate a light resonance at a plurality of wavelengths. For example, an etalon of physical length L has resonance at a wavelength of 2 L, which is an integral multiple of 2. It should be noted that in this example, the wavelength follows the material from which the interior of Etalon is produced. Therefore, when a set of wavelengths is selected for the resonance of the resonator, there may be optimal operating conditions in the WDM system. In various examples, the optical resonator may be designed and manufactured in various dimensions to accommodate a particular set of desired wavelengths for a WDM system. Moreover, in some examples, the optical resonator is adjustable and / or piezoelectric that allows adjustment of various dimensions, for example by positioning at different angles with respect to incoming light, or, for example, by electrical signals. It may be further adjusted after manufacture by including various characteristics such as sex or other materials.

In addition to multiple wavelengths that interact independently of each other, the different polarizations of each wavelength also behave independently of each other in different optical cavities. Therefore, an optical system according to the contents described herein can accommodate different modulation schemes for different polarizations of different wavelengths. For reference, polarization is usually determined with respect to the direction of the electric field of the optical signal.

FIG. 6 shows a WDM receiver portion 600 that receives a plurality of polarized signals at one or more wavelengths. The incoming light 602 includes a plurality of wavelengths, each wavelength potentially having a plurality of orthogonally polarized waves such as horizontal (H) and vertical (V). The coupling of each wavelength polarization may have any of the various modulation schemes associated with it. In some examples, the incoming light 602 may pass through various optical systems 616 and be directed at an optical resonator such as the Etalon 604. The coupling of each wavelength polarization of light 606a emitted from Etalon 604 includes intensity variations that represent various modulation transitions. In particular, the electric field at each wavelength approaches or reaches the steady-state intensity at the output of Etalon 604, which is independent of the electric fields at other wavelengths. Phase or other modulation in one or more of the incident electric fields changes the output intensity for each of the affected electric fields. The direction of the electric field, that is, the polarization, is not changed by Etalon 604.

The synchrotron radiation 606a may pass through the additional optics 614 to provide, for example, focusing light 606b, and enter a waveguide grid 608 (such as an arrayed waveguide grid). The waveguide grid 608 separates the individual wavelengths and provides each wavelength of light 610 as an input to one or more polarization beam splitters 618. Each polarization beam splitter 618 splits its wavelength into horizontal and vertical components, thereby providing two optical signals 620 for each wavelength of light 610. An array of one or more detectors 612, eg, photodetectors, may, for example, convert each wavelength-separated polarized light signal 620 into an electrical signal for further processing.

In some examples, the waveguide grid 608 may be a fiber coupled to a polarization beam splitter 618. Further, the output of the polarization beam splitter 618 may be a fiber coupled to various detectors 612. In some examples, not all wavelengths have multiple polarizations, and the polarization beam splitter may be omitted for wavelengths that have only a single polarization. In some examples, not all wavelengths of resonance provided by the Etalon 604 (or other optical resonator) are used.

FIG. 7 shows an example of a WDM system 700 including a transmitting unit 710 and a receiving unit 720 coupled by a communication channel 730. The transmitter 710 includes a number of light sources 712, such as lasers, that generate light signals of varying wavelengths. The output of each light source may be modulated by one of a plurality of modulators 714 and polarized by one of a plurality of polarizations 716 according to various data streams (eg, communication data). The various optical signals are multiplexed together by a multiplexer 718 to become a WDM signal (eg, an optical signal with multiple wavelengths carrying different information) transmitted on channel 730. Since the various polarized wavelengths do not interfere with each other, the multiplexer 718 may, in some examples, be an optical combiner or lens that focuses various optical signals for coupling, eg, into a fiber optic cable. Therefore, channel 730 may be a fiber optic cable in some examples. In some examples, the channel may include a free space medium.

The receiver 720 may include, for example, a large number of instances of the receiver portion 600 of FIG. The beam splitter 722 may disperse the light coming from the channel 730 into a plurality of such receiver portions, each of which may have a different configuration of the optical resonator 724. In some examples, only a single receiver portion may be required. In another example, multiple receiver portions with different configurations of the optical resonator 724 may be provided, as shown in FIG. For example, the optical resonator 724a may be designed and / or tuned to receive a subset of the transmitted wavelengths, while the optical resonator 724b is designed to receive a different set of transmitted wavelengths and / Or may be adjusted. As an addition or alternative, different optical resonators 724 may be designed to operate in different modulation schemes. For example, the optical resonator 724a may be designed (eg, optimized) for Binary Phase Shift Keying (BPSK) modulation, while the optical resonator 724b may be quadrature phase shifted. It may be designed for Quadrature Phase Shift Keying (QPSK) and the optical resonator 724c may be designed for Quadrature Amplitude Modulation (QAM) of the changing constellation. In some examples, any of the optical resonators 724a, 724b, 724c may include a plurality of optical resonators, for example, to accommodate higher order modulation schemes.

As in FIG. 6, the receiver portion 720 may include a detector to output an amplitude-modulated electrical signal, with any one amplitude modulation of the electrical signal being modulated at a particular wavelength and associated with it. Represents the polarization. The electrical signal is provided to the additional receiving component 726 to interpret the amplitude variation and restore the information carried by the modulated polarized light signal generated by the transmitter 710.

It should be understood that the various disruptions in output intensity caused by the modulation of the incoming optical signal are the dimensional length of the etalon or microring, the physical dimensions of the optical resonator, such as the size of the etalon, and which of them. It may vary with how accurately it was manufactured, for example, how well the etalon was tuned to one or more wavelengths. The output intensity from an etalon with a smaller dimensional length is more confused by the transition in the input signal than the etalon with a larger dimension, and the steady state is reestablished sooner after such a transition. Moreover, compared to etalons manufactured to less accurate tolerances, etalons tuned to more accurate tolerances, i.e. to a particular wavelength (or to a set of wavelengths), have higher resonance in steady state. It provides the output signal strength and shows better sensitivity to transitions in the input signal.

Various embodiments may have different etalon dimensions and tolerances based on specific design criteria and to accommodate changing operating characteristics. In some examples, the various etalon dimensions and margins are how powerful and / or how quickly the etalon responds to the transition of the incoming optical signal, such as the phase transition associated with phase modulation, and the transition. It may be chosen to trade off and balance how quickly Etalon approaches steady state after. In addition, the various etalon dimensions and margins of error may be selected to optimize the receiver, such as the receiver 200, for a particular data rate and / or a particular wavelength.

The various dimensions of the optical resonator according to the aspects and examples disclosed herein may be significantly smaller than the dimensions related to the baud rate or symbol length of the phase-coded optical signal. In some examples, the resonant dimensions (eg, etalon length, microring loop length, etc.) may provide an effective optical length that is less than half the hometown associated with the baud rate or symbol length. For example, the baud rate may be the rate at which the modulation variation occurs, and the symbol length may be the distance at which the optical signal propagates during the modulation variation. In the case of an optical resonator, the distance at which the optical signal propagates may be based on the material or optical medium in which the optical resonator is constructed. In an optical cavity such as an etalon or microring, which can store and provide resonance through interfering with each other and strengthening and weakening the optical signal energy, the optical signal energy stays in the cavity for more time. Remain. As a result, the effective optical length is longer than the physical length of the resonator. That is, the optical signal energy spends more time in the resonator than if the resonator resonates and passes the optical signal without accumulating. Therefore, the time to the next modulation variation (ie, the reciprocal of the baud rate) can be sufficient time for the incoming optical signal to pass through the resonant dimensions of the optical cavity many times. In a particular example, the resonant dimensions (etalon length, loop length) may provide an effective optical length of one-third or less of the symbol length. In some examples, the physical dimension of the etalon length or loop length may be as much as one tenth of the symbol length (eg, depending on the reflectance of the etalon surface) and one third of the symbol length. Provides an effective optical length. Therefore, according to aspects and examples that can accommodate the wide range of modulation rates described above, the symbol length may be as long as or greater than 5000 times the physical dimensions of the etalon or loop length. Further, the symbol length may be about 5000 times or more the physical dimension of the etalon or loop length, depending on aspects and examples that can accommodate a wide range of modulation rates as described above.

Additional benefits associated with the use of optical cavities such as etalons or microrings, such as front-end components coupled with processing subsystems for the reception of modulated optical communication signals, are free space or fiber coupling or other. Includes flexible operation in which signals can be received via optical waveguides and / or components. Optical cavities may also provide noise reduction by rejecting optical signal energies that are not of the intended wavelength, for example by resonant measurement. In addition, the optical resonator may be provided with a coating or other feature to further reject unwanted optical wavelengths, including alternative resonant wavelengths that are not intended to be part of the received communication signal. For example, a particular length (or width, depending on perspective) of an optical component may resonate at multiple wavelengths, but coatings and / or other design features accumulate optical signal energy at unwanted wavelengths. It may act to limit. For example, a coating that provides reduced reflectance at alternative wavelengths, or a filter that is integrated into or placed in front of a hole in the optical cavity.

Additional modulation formats may also be accommodated by the particular design features of the optical resonator. Resonant properties may respond to pulse width or other modulation in addition to pure phase transitions. For example, a pulse width modulated signal stores signal energy trapped in a resonator and approaches a steady state value. The longer the pulse width, the closer the resonator is to the steady-state signal energy condition, or the longer it stays in the steady-state signal energy condition. When the pulse stops, the output of the optical resonator changes in the same way as a phase transition. Therefore, the amplitude and pulse width modulation of the incoming light signal may be detected by processing the light intensity output of the optical resonator.

As described above with reference to FIGS. 1 and 2, in various examples, the components of transmitter 100 and / receiver 20 are analog circuits, digital circuits, or one or more digital signal processors that execute software instructions. (Digital signal processors: DSP) or one of other microprocessors or a combination thereof. Software instructions may include DSP instructions.

FIG. 8 shows an example of a control circuit (eg, control unit 800) capable of implementing software routines corresponding to various components and / or other components of a transmission system as shown in FIG. The control unit 800 may further implement software routines corresponding to the receiver component and / or other components of the receiver 200, such as the digital processing subsystem 250 of FIG. The control unit 800 may include a processor 802, a data store 804, a memory 806, and one or more interfaces 808, such as a system interface and / or a user interface. Although not explicitly shown in FIG. 8, in certain examples, the control unit 800 may be coupled to a power source. The power supply may supply power to one or more components of the control unit 800 and other components of the optical transmitter 100 or the optical receiver 200.

In FIG. 8, processor 802 is coupled to data storage device 804, memory 806, and various interfaces 808. The memory 806 stores a program (eg, a sequence of instructions encoded to be made executable by the processor 802) and data during the operation of the control unit 800. Therefore, the memory 806 may be a volatile random access memory with relatively high performance, such as a dynamic random access memory (DRAM) or a static memory (SRAM). However, the memory 806 may include any device that stores data, such as a disk drive or non-volatile storage device. In various examples, the memory 806 may be organized into identified, in some examples, unique structures in order to perform the functions disclosed herein. These data structures may be sized and organized to store specific data values and data types.

Data storage device 804 includes computer-readable and writable data storage media configured to store non-temporary instructions and other data, and non-volatile storage media such as optical or magnetic disks, ROMs, or flash memory. Can include. Instructions may include an executable program or other code that can be executed by at least one processor 802 to perform any of the functions described herein.

In various examples, the control unit 800 includes several interface components 808, such as a system interface and / or a user interface. Each of the interface components 808 exchanges data, eg, transmits or receives, with other components of control unit 800 (and / or associated transmitter or receiver) or with other devices communicating with control unit 800. It is configured to do. According to various examples, the interface component 808 may include a hardware component, a software component, or a combination of hardware and software components.

In a particular example, the components of the system interface combine the processor 802 with one or more other components of the optical transmitter 100 shown in FIG. 1 or the optical receiver 200 shown in FIG. The system interface may provide one or more control signals to any such component and manage the operation of such components, as described above.

The user interface may include hardware and / or software components that allow the corresponding transmitter or receiver into which the control unit 800 is incorporated to communicate with an external entity such as a user. These components may be configured to receive information from user interactions through the user interface. Examples of components that can be used within the user interface are buttons, switches, light emitting diodes, touch screens, displays, stored voice signals, voice recognition, or applications on devices that can be run by a computer communicating with control unit 800. Including. The data received by the various interfaces may be provided to the processor 802 as shown in FIG. The communication coupling between processor 802, memory 806, data storage device 804, and interface 808 (eg, the interconnect mechanism 810 shown) is one or more physical buses that follow standard, proprietary, or dedicated computing bus technology. May be implemented as.

Processor 802 executes a series of instructions that yield manipulated data stored in and read from data storage device 804 as described above. In various examples, the series of instructions results in the interpretation of the output from the optical resonator, as described above. Such an instruction may correspond to a command that interprets a phase, frequency, or amplitude change (modulation) in an incoming optical signal and / or restores a data payload from it, as described above.

The processor 802 may be any type of processor, multiprocessor, or control unit, whether commercially available or specially manufactured. For example, the processor may include a commercially available processor such as a processor manufactured by INTEL, AMD, MOTOROLA, or FREESCALE. In some examples, processor 802 is configured to run an operating system such as a real-time operating system (RTOS), such as RTLinux, or a non-real-time operating system such as BSD or GNU / Linux. You can. The operating system may provide platform services to the application software. These platform services may include interprocess and network communications, file system management, and standard database operations. One or more of many operating systems may be used, and examples are not limited to any particular operating system or operating system characteristics.

It should be understood that by describing some aspects of at least one embodiment, various substitutions, changes, and improvements will occur immediately to those skilled in the art. Such substitutions, changes, and improvements are intended to be part of this disclosure and are intended to be within the scope of this disclosure. Therefore, the above description and drawings are used only by way of illustration.

Claims (20)

It is an optical signal receiver
An optical resonator having a hole through which the optical signal energy can enter and an output capable of radiating a part of the optical signal energy, wherein the optical resonator has optical signal energies having a plurality of wavelengths through the hole. Is received, the resonant optical signal energy is stored inside the optical resonator, the optical signal energy radiated at each of the plurality of wavelengths is brought close to the steady state output intensity, and the received optical signal energy of each wavelength is used. The transition is configured to disturb the radiated optical signal energy at each of the wavelengths, the optical cavity has at least one dimension, and the stored optical signal energy at each of the plurality of wavelengths. Optical cavities that produce phase matching,
An optical splitter configured to receive the emitted optical signal energy and separate the emitted optical signal energy into each of the plurality of wavelengths.
Detection configured to receive at least one of the plurality of wavelengths, detect the disturbance to the emitted optical signal energy, and determine the characteristics of the transition in the received optical signal energy based on the disturbance. With a vessel
Optical signal receiver including. The optical signal receiver according to claim 1, wherein the optical resonator is further configured to disturb the emitted optical signal energy based on a phase change in the received optical signal energy. The turbulence is a change in the intensity of the emitted optical signal energy, and the detector is configured to detect the change and determine a phase transition in the received optical signal energy based on the change. The optical signal receiver according to claim 1. The optical resonator is an etalon having two semi-reflective surfaces configured to at least partially trap the optical signal energy by reflecting a portion of the optical signal energy that collides with each of the semi-reflective surfaces. , The optical signal receiver according to claim 1. The optical resonator includes first and second reflecting surfaces, the first and second reflecting surfaces being substantially parallel to each other and having reflecting sides facing each other, the first reflecting surface being the hole. At least a part of the above is formed, the optical signal energy arriving from the outside of the optical resonator is partially transmitted, the optical signal energy is input to the optical resonator, and the second reflecting surface is at least the output. A part of the optical signal energy is substantially reflected, but the part of the optical signal energy is partially transmitted to the inside of the optical cavity and radiated to the outside of the optical cavity. The optical signal receiver according to claim 1, which is input to the optical resonator. The detector further comprises an opto-electrical converter configured to convert the radiated optical signal energy into an electrical signal, the optical signal having an amplitude indicating the intensity of the radiated optical signal energy. The optical signal receiver according to claim 1, which is configured to detect disturbances to the radiated optical signal energy by processing the electrical signal. A method of detecting information encoded in an optical signal, wherein the method is
The step of receiving optical signal energy of multiple wavelengths,
The step of accumulating the optical signal energy in the optical resonator that brings the accumulated optical signal energy closer to the steady state, and
In the step of outputting the optical signal energy from the accumulated optical signal energy, the intensity of the output optical signal energy at each wavelength of the plurality of wavelengths is the intensity of the accumulated light of the respective wavelengths. Steps, which are proportional to the signal energy,
The step of detecting the output optical signal energy of at least one of the plurality of wavelengths,
The step of determining the modulation characteristic of the received optical signal energy based on the detected output optical signal energy, and
How to include. The step of determining the modulation characteristic of the received optical signal energy based on the detected output optical signal energy is a step of determining the phase change of the received optical signal energy based on the intensity change of the output optical signal energy. The method according to claim 7, including. In response to the modulation characteristic of the received optical signal energy, the stored optical signal energy in the optical resonator is generated by one of the weakening interference or the strengthening interference in the optical resonator. The method of claim 7, further comprising changing steps. The method of claim 9, wherein the modulation characteristic of the received optical signal energy is a phase transition associated with each of the wavelengths. The method according to claim 7, wherein the step of accumulating the optical signal energy in the optical resonator includes a step of partially reflecting the optical signal energy between two semi-reflective surfaces. The method of claim 7, further comprising a step of converting the output light signal energy into an electrical signal, wherein the amplitude of the electrical signal represents the intensity of the output light signal energy. The method according to claim 12, wherein the step of determining the modulation characteristic of the received optical signal energy based on the detected output optical signal energy includes a step of supplying the electric signal to the receiver. It's an optical receiver
An etalon, one of a hole for inputting the optical signal energy and one of the accumulated optical signal energies, which is configured to at least partially store optical signal energies of a plurality of wavelengths between two semi-reflecting surfaces. The etalon comprises an output that radiates a portion, and the etalon is configured to temporarily change the intensity of the output optical signal energy based on the phase transition of the input optical signal energy. ,
An opto-electrical converter that receives at least one wavelength of the output optical signal energy and is configured to convert the received optical signal energy into an electrical signal.
A receiver, which is configured to receive the electrical signal and determine encoded information based in part on the electrical signal.
Including optical receiver. 14. Optical reception according to claim 14, further comprising a converter configured to convert the electrical signal from an analog format to a digital format, wherein the receiver is configured to receive the electrical signal in the digital format. Machine. The optical receiver according to claim 14, further comprising an optical splitter configured to receive the output optical signal energy and separate the output optical signal energy into each of the plurality of wavelengths. The optical receiver according to claim 16, wherein the optical splitter is an array type waveguide grid. The optical receiver according to claim 14, wherein the etalon is configured to have a reference dimension selected for storing at least partially the optical signal energies of the plurality of wavelengths in the etalon. The etalon is configured to have a reference dimension selected to cause the accumulation of optical signal energy to occur at a particular rate to correspond to the expected data rate associated with the encoded information. The optical receiver according to claim 14. The optical receiver according to claim 14, further comprising an optical system configured to collect optical signal energy and supply the optical signal energy to the etalon.

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